Word Origin & History

infect late 14c., from L. infectus, pp. of inficere "to spoil, stain," lit. "to put in," from in- "in" + facere "perform" (see factitious). Infection is 1548 in sense of "communication of disease by agency of air or water" (distinguished from contagion, which is body-to-body communication). Infectious "catching, having the quality of spreading from person to person" is 1542 of diseases, 1611 of emotions, actions, etc.